This proposal addresses the fundamental issue of what aspects of the speech production mechanism people might control when they talk. It is concerned with the discovery of a set of time-varying articulatory parameters that are used for vowels in the languages of the world. A special area of study will be the dynamic articulatory movements that occur in diphthongs, because they constitute an important test case for studies on timing in speech. Other studies will investigate the degrees of freedom involved in the movements of the lips, the jaw and the tongue. This will lead to investigating the extent to which identical vocal tract shapes can be produced by different articulatory combinations. Additional studies will elucidate the content of the much used but ill-defined notion of "base of articulation". Finally, the extent to which consonants and vowels are controlled by the same articulatory system will be brought into question. As an alternative to current views it will be shown that the same controlling parameters underlie both consonant and vowel gestures. The proposed studies will also make significant contributions to methodological issues involving the use of x-ray microbeam data. Algorithms will be devised for comparing dynamic articulatory data obtained from one individual with that obtained from another. A wide variety of languages will be used, leading to a better understanding of variation in natural languages, thus elucidating the notion of what can be considered normal and abnormal in speech.